Present day CMOS integrated circuits use a 5 volt power supply. As the size of the CMOS devices are reduced, the voltage that the device can tolerate is similarly reduced. Consequently, a smaller power supply voltage will be needed to accommodate the smaller CMOS devices.
In order to maintain compatibility with CMOS integrated circuits using a 5 volt power supply, as well as other technologies such as bipolar and ECL, it is desirable that the new CMOS integrated circuits also use a 5 volt power supply at its external pins. Internally, however, it is necessary to provide a smaller voltage, such as 2.5-3.0 volts for the CMOS devices.
One alternative is to use an on-chip voltage regulator which is powered by 5 volts and outputs a smaller voltage, such as 2.5 volts. Such an arrangement is inefficient since the excess voltage would be dissapated as heat, and is therefore undesirable from both a power and a reliability standpoint.
Therefore, a need has arisen in the industry to provide an integrated circuit having a 5 volt power supply input which efficiently supplies the CMOS devices comprising the integrated circuit with a reduced voltage.